1. Field of the Invention
This invention relates generally to new polypeptides and more particularly to closely related new polypeptides isolated in purified form from the bovine thymus, to methods for isolation of these new polypeptides, and therapeutic fields of use for the polypeptides.
2. Description of the Prior Art
It is well known that polypeptides have been isolated from various organs or animals. Until about the past decade, however, very little was known about the thymus, an organ which in man comprises about 0.8% of his body weight at birth, although it has been previously hypothesized that a neuromuscular blocking substance existed in the thymus. Despite keen interest in possible functions of the thymus and early speculation and experimentation, little was known of the function of the thymus until recently. It is now realized, however, that the thymus is a compound organ with both epithelial (endocrine) and lymphoid (immunological) components and thus the thymus is involved in the immunity functions of the body. The thymus is known to be a compound organ consisting of an epithelial stroma derived from the third bronchial arch and lymphocytes derived from stem cells originating in haemopoietic tissues, Goldstein et al., The Human Thymus, Heinemann, London, 1969. Lymphocytes are differentiated within the thymus and leave as mature thymus-derived cells, called T cells, which circulate to the blood, lymph, spleen and lymph nodes. The induction of stem cell differentiation within the thymus appears to be mediated by secretions of the epithelial cells of the thymus but difficulties with bioassays have hindered the complete isolation and structural characterization of any hormones which may be present.
It has been known for some time that the thymus is connected with the immunity characteristics of the body and therefore great interest has been indicated in substances which have been isolated from the thymus. In this regard, there have been published in recent years a relatively large body of articles based on scientific work relating to materials which are present in bovine thymus. In fact, the Applicant has published a number of articles which relate to his research in this area. Pertinent publications may be found for example in The Lancet, July 20, 1968, pps. 119-122; Triangle, Vol. 11, No. 1, pps. 7-14, 1972; Annals of the New York Academy of Sciences, Vol. 183, pps. 230-240, 1971; and Clinical and Experimental Immunology, Vol. 4, No. 2, pps. 181-189, 1969.
In the article by Goldstein and Manganaro in Annals of the New York Academy of Sciences, Vol. 183, pps. 230-240, 1971, there are disclosures regarding the presence of a thymic polypeptide which causes a myasthenic neuromuscular block in animals, which is analogous to the human disease of myasthenia gravis. Further, in this article it was discovered that two distinct effects were caused by separate polypeptides in bovine thymus. One of these polypeptides, named "thymotoxin", was believed to cause myositis but it was further indicated that this polypeptide had not been isolated although it appeared to be a polypeptide of approximately 7,000 molecular weight, had a strong net positive charge and was reatined on CM-Sephadex at a pH of 8.0.
It was further disclosed that small amounts of a material named "thymin" had been detected in bovine thymus using saline extraction, heat treatments, centrifugation, ion exchange chromatography, molecular sieving on Sephadex, hydroxyl apatite chromatography and preparative polyacrylamide electrophoresis. At page 235, it was indicated that neuromuscular blocking activity had been detected in a polypeptide fraction of approximately 7,000 molecular weight and that doses of 0.2 milligram of this material injected subcutaneously in 200 gram rats caused myasthenic neuromuscular block at five days as demonstrated by electromyography. The polypeptides of the present invention are not disclosed by these prior art disclosures.
It will be apparent from the above articles and the various publications which are cited in these articles that a large amount of work has been done in the isolation and identification of materials from bovine thymus. However, in none of these articles has there been disclosed the isolation of pure materials which are highly pure polypeptides which can now be characterized by definite chemical and physical properties and which have been isolated in a form which did not exist in the bovine thymus from where they were obtained. Further, the new polypeptides isolated from bovine thymus in accordance with this invention exhibit physiological characteristics which suggest that they are important to medical science in the study of the immunity system of the human body and have many therapeutic applications.